1. Field of the Invention
This invention relates to an oil gauge for a cartridge-type oil tank, and more particularly to an oil gauge for a cartridge-type oil tank which is used for an oil burner or the like.
2. Description of the Prior Art
An oil tank which has been conventionally used for an oil burner or the like is generally classified into two types or a cartridge-type and an open-type. A cartridge-type oil tank is used in an inverted manner, resulting in negative pressure being constantly applied to an interior of the cartridge-type oil tank during the use. Accordingly, the deterioration of airtightness of the tank causes leakage of oil stored in the cartridge-type oil tank. Thus, arrangement of an oil gauge in the oil tank must be carefully carried out while ensuring airtightness of the tank. Also, an oil gauge for a cartridge-type oil tank is required to indicate the amount of oil int he tank both when use of the tank and during oil is fed tot he tank. In view of such requirements, a conventional oil gauge for a cartridge-type oil tank is typically constructed as shown in FIGS. 1A and 1B wherein FIG. 1A shows a cartridge-type oil tank to which oil feed has been completed and FIG. 1B shows the tank which has become substantially empty during the use. As shown in FIGS. 1A and 1B the conventional oil gauge substantially comprises only a transparent window A provided on a side wall of the cartridge-type oil tank B, through which a level of oil in the tank is viewed.
The conventional oil gauge has a disadvantage of failing to indicating the actual amount of oil stored in a cartridge-type oil tank although it acts as a qualitative oil indicator both during use of the tank and during oil feed to the tank.
In view of such a disadvantage, the inventor proposed an oil gauge for a cartridge-type oil tank as disclosed in Japanese Utility Model Application Nos. 182563/1984, 182564/1984 and 182565/1984 which were filed on Nov. 30, 1984, assigned to the assignee, and laid-open to public inspection on June 30, 1986 under Japanese Utility Model Application Laying-Open Publication Nos. 101232/1986, 96329/1986 and 97729/1986, respectively. The oil gauge taught in Japanese utility Model Application No. 182563/1984 is constructed in a manner to mount a pointer on an arm rod and vertically move an indicator plate by gravity. However, the oil gauge fails to ensure its smooth operation due to a failure in preventing entrance of dust or the like therein. In the oil gauge disclosed in Japanese Utility Model Application No. 182564/1984, an arm rod and an indicator are pivotally mounted on a gauge base so as to be pivotable in a cartridge-type oil tank and the indicator is moved in relation to the arm rod by means of a stopper means provided on the arm rod. However, the oil gauge is insufficient in strength because the arm rod and indicator each are supported in a manner like a cantilever. Also, it has another disadvantage that its parts must be manufactured with high precision, to thereby significantly increase the manufacturing cost. Thus, the oil gauge failed to be put to practical use. The oil gauge taught in Japanese Utility Model Application No. 182565/1984 is so constructed that an indicator is mounted on an arm rod and provided with two scales or a first scale used during the use and a second one used when oil is fed to a cartridge-type oil tank. Unfortunately, the oil gauge has a disadvantage of failing to prevent entrance of dust or the like therein, to thereby deteriorate its smooth operation, like that taught in Japanese Utility Model Application No. 182563/1984 described above.
Accordingly, it would be highly desirable to develop an oil gauge for a cartridge-type oil tank which is capable of positively indicating the actual amount of oil in the cartridge-type oil tank with a simple structure while ensuring airtightness for both the oil tank and oil gauge and providing the oil gauge with rigidity or sufficient mechanical strength